Field of the Invention
The present invention relates to a lens driving apparatus, and more particularly, to an image blur correction apparatus using a plurality of ultrasonic motors, and a lens apparatus and an image pickup apparatus including the same.
Description of the Related Art
Hitherto, there is known a technology of driving a lens in a direction perpendicular to an optical axis of a lens system to reduce influences of camera shake occurring at the time of photographing a video image in a camera module including the lens system and an image pickup element, which is mounted in a camera for acquiring video images. In optical systems having the image stabilization function described above, the lens is required to be driven at high speed with high accuracy in the direction perpendicular to the optical axis. Therefore, a large number of image blur correction apparatus, each including a voice coil motor, have been proposed.
In this context, image blur correction apparatus using ultrasonic motors, each utilizing oscillations of an oscillator such as a piezoelectric element, have been proposed in recent years for the purpose of further enhancing the accuracy. Specifically, a plurality of ultrasonic motors are arranged to combine drives thereof such that a movable body can be moved in a two-dimensional direction, thereby realizing a two-dimensional driving apparatus. The thus realized two-dimensional driving apparatus is used for the image blur correction apparatus. As one of the image blur correction apparatus described above, the following configuration of the image blur correction apparatus has been proposed.
In Japanese Patent Application Laid-Open No. 2014-14256, a plurality of oscillators are fixed to a fixed barrel. A lens moving frame including a driven body is pressed against the oscillators to be brought into contact therewith from the above through intermediation of mechanical coupling, thereby transmitting driving forces of the oscillators to the lens moving frame.
The ultrasonic motor mechanically transmits the driving force. Therefore, as compared with the voice coil motor that transmits the driving force by using a magnetic force, high positional accuracy is required for the lens moving frame and the ultrasonic motors. In Japanese Patent Application Laid-Open No. 2014-14256, the oscillators are fixed on the fixed barrel in advance. Thereafter, the lens moving frame including the driven body is positioned with respect to the oscillators. Thus, it is inevitable to simultaneously perform a plurality of positioning operations that require high accuracy as described above, which prevents easy assembly.
Further, the oscillator included in the ultrasonic motor wears along with the use, and therefore characteristics of the image blur correction apparatus are lowered due to the wear. In such a case, the ultrasonic motor is required to be replaced or repaired. According to the configuration described in Japanese Patent Application Laid-Open No. 2014-14256, however, the ultrasonic motor cannot be directly removed. Therefore, it is inevitable that the image blur correction apparatus is disassembled to remove the lens moving frame, and then, a plurality of positioning operations are performed again after the replacement of the ultrasonic motor, which results in reduced ease of maintenance.